CZ68194A3 - Matt, biaxially stretched polypropylene foil and process for producing thereof - Google Patents

Abstract

The invention relates to matt, multilayered propylene films which receive their matt appearance by a one-sided, coextruded layer of a polymer mixture.

Description

The invention relates to matt, multilayer polypropylene films which obtain their matt appearance by at least one coextruded layer of polymer blend.

BACKGROUND OF THE INVENTION

A large number of matt, biaxially stretched polypropylene films are already known.

DE-A 3 231 013 specifically describes a polypropylene film with a misted surface, which is produced by subjecting the film to irradiation with high-energy radiation before stretching.

JP 9 148 661 discloses a method by which sandblasting or chemical etching processes produce a hazy surface on a biaxially stretched polypropylene film.

An increasing semi-opacity by adding organic peroxides to propylene and ethylene block polymers and to polyethylene based copolymers is described, for example, in JP 2 103 214.

In contrast, according to the process described in DE-A 3,839,120, 5-10% of the inorganic fillers added over the entire thickness of the oriented polypropylene film cause a hazy surface.

A one-sided matt overlay of an inorganic and / or organic matting agent with an ester resin that is applied from organic solvents is described in EP-A 262 953.

The contaminated surfaces are produced according to JP 8 038 157 and JP 3 129 264 using polypropylene α- and β spherulites.

Many patents disclose matt films in which the matt effect is induced by propylene-ethylene block polymers or by blends of polypropylene homopolymers and / or polypropylene / polyethylene copolymers.

JP 6 032 668 describes, for example, non-shiny, biaxial polypropylene films which, over the entire film thickness, consist of a blend of polypropylene with 10 to 65% polyethylene.

A multilayer film with a low surface gloss is produced by laminating a monoaxially stretched polypropylene film using a mixture of propylene / ethylene / High Density polyethylene copolymers and subjecting the laminate to transverse stretching (JP 8 001 525).

EP-A 122 495 discloses at least a two-layer, biaxially stretched polypropylene film in which at least one layer consists of a polyolefin with an ethylene content of 10 to 50% by weight. As an example, a block polymer of ethylene and propylene with three melting regions between 120 and 160 ° C is described.

EP-A 44 544 discloses a multilayer, stretched polypropylene film with a two-layer polypropylene structure, to which a monoaxially or biaxially stretched propylene-ethylene block polymer layer is additionally applied. In addition, there is a choice of an additional adhesive layer.

A non-shiny, laminated film produced by biaxial stretching of polypropylene containing 10 to 50% by weight of ethylene is disclosed in JP 0 184 840.

Also in JP 0 054 783 it describes a biaxial stretch film having a misted surface under the influence of a propylene-ethylene block copolymer.

DE-A 4 209 918 describes a film construction in which a matt layer of a propylene-ethylene block copolymer, a propylene-ethylene (butylene) random copolymer or a random terpolymer, (butylene) copolymer or (butylene) terpolymer based on ethylene, which has been modified with polar groups and optionally still contains polyamide.

Matt surfaces can also be obtained by laminating unilaterally stretched copolymers of ethylene and propylene to a biaxially stretched polypropylene film.

Methods for producing biaxially stretched polypropylene films are in part very expensive or are associated with high investments (eg etching, sandblasting, electron irradiation, painting). Other films do not meet the market requirements with regard to the optical properties, the adjustability or the printability of the matt layer.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to meet the requirements of the market and to produce matt films on existing biaxially stretched polypropylene coextrusion plants.

Accordingly, the present invention provides matt, bilayer or multilayer biaxially stretched polypropylene films from one outer matt layer vrstvy, the base layer K and optionally other layers S which are attached to the base layer on the opposite side to the matt layer as well as polymer blends. from which the matt layer may be made, the matt layer M having a thickness of 0.5 to 5.0 gm and consisting of

- 75% of one or more block copolymers of polypropylene and polyethylene,

- 15% of ethylene-based copolymers or terpolymers, • modified by polar groups and elastomeric components,

- 40% of random copolymers and / or terpolymers based on propylene / ethylene / butylene with propylene as the main component,

- 20% high density polyethylene, and

- 2% natural or synthetic silicic acid, the above components being used as supplied and / or in the form of a masterbatch, the base layer K consists of a thermoplastic polymer and / or a propylene copolymer, which may be equipped with conventional glidants, antistatic agents and / or anti-blocking agents, and the layers S located on the base layer K opposite the matt layer consist either of thermoplastic polypropylene, which may be equipped with conventional glidants, antistatic agents and / or anti-blocking agents, and / or a thermoplastic random copolymer of polypropylene with one or more C 2 -C 6 α-olefins, which may be equipped with conventional glidants, antistatic agents and / or anti-blocking agents, or a hot-laminated layer of a mixture of ethylene-based copolymers or consisting of of a combination of the above layers.

The following substances are used as starting materials for the matt layer M:

Copolymers of propylene made from propylene and α-olefins, preferably ethylene, by a block polymerization process, or heterophasic copolymers of ethylene and propylene, or rubber modified polypropylene or PP-block copolymers and reactor mixtures.

2. Linear copolymers of low density ethylene that are modified and / or low density polyethylenes that are modified with rubber and have anhydride functionality and / or terpolymers of ethylene with acrylic esters and maleic anhydride.

3. Statistical copolymers of propylene and ethylene with 2 to 6% by weight of ethylene or statistical terpolymers of propylene, ethylene and butylene with a comonomer content of <15% by weight and a butylene content of <7% by weight.

4. High density polyethylene in the region of 0.94 to 0.965 and with a melt index of 0.3 to 5 g / min at 190 ° C and a load of 50 N.

5. Synthetic and / or natural silica / SiO2 particles <10 gm.

The following materials are used as starting materials for the base layer K:

- isotactic polypropylene having a fraction soluble in n-heptane of 15% by weight or less, a density of 0,90 to 0,91 g / cm cm and a melt index of 0,5 g / 10 min at 230 ° C and a load of 21,2 N (determined according to DIN 53735), particularly preferably polypropylene having a melt index of 1 to 4 g / 10 min, and / or

- a random copolymer of propylene and ethylene with 2 to 6% by weight of ethylene, preferably having a density of 0.895 to and

0,960 g / cm, with a melt index of 1 to 7 g / 10 min at 230 ° C and a load of 21,2 N and a melting point of crystallites, depending on the type, between 125 and 140 ° C (under a polarizing microscope), and / or

- a copolymer of propylene, butylene and ethylene with a comonomer content preferably <15% by weight and a butylene content preferably <7% by weight, preferably with a melt index of 0.1 to 16 g / 10 min at 230 ° C and a load of 21.2 N, especially preferably 4 to 10 g / 10 min at 230 ° C and a load of 21.2 N.

The following materials serve as starting materials for the S-layers:

isotactic polypropylene and / or random copolymers and / or terpolymers, which also serve as starting materials for the base layer and / or a composition for use in hot lamination, which in a preferred embodiment consists of ethylene vinyl acetate copolymers A and at least one other copolymer of a group of ethylene-ethyl acrylate copolymers B1 or a group of copolymers B2 based on ethylene and acrylic acid.

The ethylene vinyl acetate copolymer A contains in a preferred embodiment 70 to 95% by weight, in particular 75 to 95% by weight, of polymerized ethylene units, in a particularly preferred embodiment, the residual part consisting essentially or entirely of polymerized vinyl acetate.

The ethylene-ethylacrylate copolymer B1 comprises in a preferred embodiment a substantially polymerized ethylene unit, in particular at least 88% by weight of polymerized ethylene units, particularly preferably 88-92% by weight of polymerized ethylene units, the residual proportions consisting essentially or entirely of polymerized ethyl acrylate.

The ethylene-acrylic acid copolymer B2 preferably consists essentially of polymerized ethylene units, in particular at least 85% by weight of polymerized ethylene units, particularly preferably 85 to 95% by weight of polymerized ethylene units, the residual proportions consisting essentially of or entirely of polymerized acrylic acid.

The ethylene vinyl acetate copolymer A preferably has a melt index of 0.1 to 15 g / 10 min at 230 ° C and at 21.2 N, particularly preferably 0.3 to 8 g / 10 min at 230 ° C and at 21.2 N .

Films of this type are produced by first coextruding a three-layer film. This co-extruded film is cooled after leaving the extrusion slot nozzle so that the matt layer is cooled as slowly as possible. Thereafter, the film is reheated to about 100 to 130 ° C and longitudinal stretching is performed in a ratio of 3 to 7, preferably 4 to 5. After longitudinal stretching, a transverse stretching in the ratio of 7 to 12, preferably 8 to 9, is carried out at a temperature in the range of 150 to 170 [deg.] C. This film is thermofixed before leaving the drawing tunnel. with Corona or flame pre-treated.

An alternative to the above-described production method is the production of a four-layer film by a three-layer coextrusion of the matt layer Μ, the base layer K and the need for a layer S which is initially lengthened together longitudinally as previously considered. Between the exit of the longitudinal drawing part and the entry into the transverse drawing part, as described in EP A2 0 424 761, lamination or extrusion with an additional layer S now proceeds. After this layer is applied, the transverse stretching of the joined films is carried out in a ratio of 1: 7 to 1: 12, preferably in a ratio of 1: 8.5 to 1: 9.5, followed by, as usual, thermofixation and Corona treatment or flame pre-treatment.

It was surprising to those skilled in the art that the addition of high density polyethylene, within the indicated concentration ranges, to mixtures of PP-PE block copolymers and random copolymers and to modified ethylene could permanently increase the matt effect of coextruded, biaxial polypropylene films.

The ethylene-based copolymers or terpolymers used, which are not polar groups and which are modified by elastomers, are normally used as interlayer adhesion promoters for the bonded films in order to join two non-adhesive polymer layers.

In such joints, the adhesion promoter layer does not affect the optical properties. The values for haze and clarity of the foil do not change.

As a component in the matt layer lying on the surface of the foil, they reduce the gloss, which is responsible, among other things, for the matt appearance of biaxially stretched foils.

Said formulations which are the subject of the present invention lead to a matt appearance when the films are biaxially stretched.

In addition, in biaxially oriented polypropylene films which have been produced with a matt layer according to the specified recipes, the thickness of the matt layer can vary within a wide range without altering the optical properties. Even with a layer thickness of less than 2 μια, matt films are obtained.

The films of the present invention preferably have a total thickness of 10 to 40 gm.

Matt thickness 1

- 75%

- 15%

- 40%

- 20%

The 2% M layer is characterized by up to 4 gm and consists preferably of a block copolymer of polypropylene, an ethylene-based copolymer or terpolymer modified with polar groups of a propylene-ethylene-based random copolymer having an ethylene content of 2 to 6 % high-density polyethylene and natural silicic acid.

The base layer preferably has a thickness of 9 to 39 gm and consists of

- 100% isotactic polypropylene having a melt index of 0.5 to 8 g / 10 min (230 ° C / 21.2 N), and

- 0% glidants, antistatic agents and / or anti-blocking agents.

The layers S are preferably either 0.5 to 1.5 μπι thick and consist of

- 100% isotactic polypropylene with a melt index of 0,5 to 8 g / 10 min (230 ° C / 21,2 N), or a random copolymer of propylene and ethylene with 3 to 5% ethylene and a melt index of 3 to 16 g / 10 min (230 ° C / 21.2 N) or a random terpolymer of propylene, ethylene and butylene with a comonomer content <12% and a melt index of 3 to 16 g / 10 min (230 ° C / 21.1 N), and

0% glidants, antistatic agents and / or antibiotic agents.

or the layers preferably have a thickness of 3 to 15 μιη and consist of

65 - 95% copolymer of ethylene and 10 - 35% copolymer of ethylene and 8 - 30% copolymer of ethylene and

vinyl acetate, ethyl acrylate and acrylic acid.

Fields of application

The films of the present invention find use as adhesive films or thermally laminated films for the graphics industry or as hot-set films for making bags or for making bonded films.

DETAILED DESCRIPTION OF THE INVENTION

The following test methods and methods for determining values and properties are used in the following examples:

The gloss is determined according to ASTM D 2457. It is the proportion of light in GE gloss units reflected at 45 ° relative to the black glass mirror as standard = 100 GE.

Haze is determined according to ASTM D 1003. It is given in% and is the ratio of diffuse light transmission to total light transmission, multiplied by 100.

Used substances for matt layers:

Polymer 1

Block copolymer PP / PE

Melting index (230 ° C / 21.2 N)

Melting point (DSC)

Elasticity modulus (DIN 53457) g / 10 min 162 ° C 1300 N / mm ²

Polymer 2

LDPE modified with elastomer and acid anhydride

Melting index (230 ° C / 21.2 N) Melting point (DSC)

Polymer 3

4.3 g / 10 min 104 ° C

LLDPE modified with elastomer and acid anhydride

Melting index (230 ° C / 21.2 N) Melting point (DSC)

Polymer 4

6.2 g / 10 min 125 ° C

P / E random copolymer s

1000 ppm SiO2

Melting index (230 ° C / 21.2 N) Melting point (DSC)

4.7 g / 10 min 140 ° C

Polymer 5

High density polyethylene with a density of 0.956 g / cm

Melting index (190 ° C / 50 N) 1.6 g / 10 min

Melting point (DSC) 130 ° C

Polymer 6

Isotactic polypropylene with n-heptane soluble content = with 6%

Melting index (230 ° C / 21.2 N)

3.3 g / 10 min

Polymer 7

Mixture of 65 - 95% ethylene / vinyl acetate copolymers

- 35% of ethylene / ethyl acrylate copolymers and 8 - 30% of ethylene / acrylic acid copolymers.

He did

The 1/3/5/4 polymer blend in a ratio of 55/10/15/20 is processed to a masterbatch. This masterbatch is a matt layer and coextruded with a polypropylene layer that is substantially free of antiblocking agents but contains lubricants and antistatic agents as additives and a second polypropylene layer equipped with antiblocking agents. Longitudinal stretching is then carried out in a ratio of 1: 4.5, after which transverse stretching takes place in a ratio of 1: 9. Corona preprocessing is performed on the non-matt side of the film. The film has a thickness of 15 μιη. The matt layer is 2.3 gm ± 0.1 gm, the base layer 11.7 gm and the S layer 1.0 gm. The foil is used for adhesive laminating of printed products.

Example 2

The foil structure and process conditions are the same as described in Example 1. However, a mixture of 1/3/5/4 polymers in a ratio of 60/10/10/20 is chosen for the matt layer M.

Example 3

The foil structure and process conditions are the same as described in Example 1. For the matt layer M, however, a mixture of polymers 1/2/5/4 in a ratio of 60/10/10/20 is chosen.

Example 4

A matt layer of a 1/3/5/4 polymer blend in a ratio of 65/10/5/20 is coextruded with a polypropylene layer that is virtually free of additives and a polymer 4 melt layer with conventional additives such as antiblocking agents, antistatic agents and lubricants. Longitudinal stretching is then carried out in a ratio of 1: 5 and further transverse stretching is performed in a ratio of 1: 9. At least one-sided corona treatment is carried out before winding. The film has a total thickness of 20 gm, with a matt layer of 2.3 gm, a polypropylene layer of 16.7 gm, and a builder layer of 1 gm. This film is suitable, inter alia, for printing, making bags on horizontal and vertical tubular bag machines and, in printed or unprinted form, as a starting film for various laminated films.

Example 5

A matt layer of a 1/2/5/4 polymer blend in a ratio of 65/5/10/20 is coextruded with a polypropylene layer that is virtually free of anti-blocking agents but contains lubricants and antistatic additives. The longitudinal drawing is then carried out in a ratio of 1: 5, followed by lamination or hot-extrusion lamination of the mixture 7 as described in EP 0 424 761. After this layer is applied, the film is stretched transversely at a ratio of 1: 9.

The hot laminated film produced in this manner has a total thickness of 22 μιη, with a matt layer of 2.5 μπι, a polypropylene layer of 12.5 μπι and a hot laminated layer of 7 μm. Such a film is used for the refinement of printing products for the graphic industry.

Example X (comparative)

The foil structure and process conditions are the same as described in Example 1. For the matt layer M, however, a mixture of 1/2/4 polymers in a ratio of 60/10/30 is chosen.

Example II (comparative)

The foil structure and process conditions are the same as described in Example 1. However, a mixture of 1/3/4 polymers in a ratio of 40/10/50 is chosen for the matt layer M.

The properties of the films produced according to the preceding examples are shown in the following table.

Claims (11)

1. A matt, bilayer or multilayer biaxially stretched polypropylene film from one outer matt layer Μ, the base layer K and optionally other layers S, which are attached to the base layer on the opposite side to the matt layer, as well as polymer blends of which the matt layer can be produced, characterized in that the matt layer M has a thickness of 0.5 to 5.0 gm and consists of 25-75% of one or more block copolymers of polypropylene and polyethylene, 5-15% of a copolymer or terpolymer based on ethylene modified with polar groups, 15-40% of a random copolymer and / or terpolymer based on propylene / ethylene / butylene with propylene as the main component, 5 - 20% high density polyethylene; and 0-2% natural or synthetic silicic acid, wherein the above components are also used as supplied and / or premixed, the base layer K consists of a thermoplastic polymer and / or a propylene copolymer, which may be equipped with conventional anti-static glidants and / or an19 tiblocking agents, and the layers S, which are located on the base layer K opposite the matte layer, consist either of thermoplastic polypropylene, which may be equipped with conventional glidants, antistatic agents and / or antiblocking agents, and / or of thermoplastic random copolymers of polypropylene having one or more α-olefins having 2 to 6 carbon atoms, which may be equipped with conventional glidants, antistatic agents and / or anti-blocking agents, or a hot-laminated layer of a mixture of ethylene-based copolymers, or assemblies and from a combination of the above layers S. A film according to claim 1, characterized in that the polypropylene of the base layer consists of isotactic polypropylene with a proportion soluble in n-heptane of 6% by weight or less. The film according to claims 1 and 2, characterized in that the block copolymers of polypropylene and polyethylene contained in the matt layer have an ethylene proportion of 6 to 8% by weight and a melt index of 3 to 6 g / 10 min (DIN 53735). Film according to claims 1 to 3, characterized in that the copolymers or the (ter) polymers contained in the opaque layer consist of polypropylene, ethylene and (butylene) and have a propylene content of more than 80% and a melt index of 3 to 6 g / 10 min (DIN 53735). Film according to one of Claims 1 to 4, characterized in that the high-density polyethylene (HDPE) contained in the matt layer has a melt index of 1 to 2 g / 10 min (DIN 53735). The film according to claims 1 to 5, characterized in that the copolymer or terpolymer contained in the opaque layer, based on polar-modified ethylene, has a melt index of 3 to 8 g / 10 min (DIN 53735 at 190 ° C). A method for the production of films according to claims 1 to 6, characterized in that the melt corresponding to the individual film layers is coextruded with a flat-slot nozzle, the coextruded film is subjected to cooling on the corresponding rolls, then the film is stretched in the longitudinal direction to a temperature in the range of 120 to 140 ° C at a factor of 35 to 5.0 and in the transverse direction at a temperature in the range of 160 to 185 ° C at a factor of 8.2 to 9.8; eventually winds up. 8. The method according to claim 7, characterized in that melt deposition or film lamination of the additional layer can be performed between the longitudinal drawing and transverse drawing phases. 9. Use of a film according to one or more of claims 1 to 8 as packaging film. - Use of a film according to one or more of claims 1 to 9 for the refinement of graphic print products, the matt side not facing the print product. Use of a film according to claim 10, characterized in that a clear UV-curable lacquer is applied on the matt side, whereby special optical effects can be achieved.